Thin film capacitor

ABSTRACT

A thin film capacitor comprises a base material, a dielectric layer provided on the base material, and an upper electrode layer provided on the dielectric layer. The dielectric layer includes a plurality of columnar crystals that extend along a normal direction with respect to a surface of the upper electrode layer, the columnar crystal has a perovskite crystal structure represented by A y BO 3 , an element A is at least one of Ba, Ca, Sr, and Pb, an element B is at least one of Ti, Zr, Sn, and Hf, y≦0.995 is satisfied, and the dielectric layer contains 0.05 to 2.5 mol of Al per 100 mol of A y BO 3 .

TECHNICAL FIELD

The present invention relates to a thin film capacitor.

BACKGROUND

An allowable mounting space for an electronic component in an electronicdevice tends to be reduced with downsizing of the electronic device. Acapacitor (frequently referred to as a “condenser” in Japan), which isan electronic component installed in the plurality of electronicdevices, is also required to be reduced in size or thinned. Since a thinfilm capacitor is thinner in a base material on which a dielectric bodyis formed, a dielectric layer, or an insulating film as compared with alaminated ceramic capacitor fabricated by the thick-film processing ofrelated art, further thinning and lowering in profile are possible.Therefore, the thin film capacitor has been expected as an electroniccomponent to be mounted on a low-profile and small space. Further, acapacitor such as those embedded in an electronic component substratehas been recently developed. In addition, development of the laminatedceramic capacitor of related art also has been advanced (see JapaneseUnexamined Patent Publication No. 2004-281446, Japanese UnexaminedPatent Publication No. 2011-228462, Japanese Unexamined PatentPublication No. 2006-196848, Japanese Unexamined Patent Publication No.2002-124712, Japanese Unexamined Patent Publication No. 2010-267953,WO2011/027625, and Japanese Unexamined Patent Publication No.2014-144881).

SUMMARY

There have been in the past many thin film capacitors having acapacitance smaller than an existing laminated ceramic capacitor. Forthis reason, for the thin film capacitor, there have been tried methodsfor improving the capacitance such as a method in which a film thicknessof the dielectric layer is made thin as much as around 300 nm or 150 nm(see Japanese Unexamined Patent Publication No. 2004-281446 and JapaneseUnexamined Patent Publication No. 2011-228462), or a method in which afine structure of the dielectric layer of the thin film capacitor ismade into not a granular structure but a columnar structure to improveferroelectricity (see Japanese Unexamined Patent Publication No.2006-196848, Japanese Unexamined Patent Publication No. 2002-124712, andJapanese Unexamined Patent Publication No. 2010-267953).

Here, the “granular structure” refers to a fine structure in which eachof crystal grains of a substance constituting the dielectric layer has aspherical shape, and the respective crystal grains are densely piled. Onthe other hand, the “columnar structure” refers to a structure in whicheach of crystal grains constituting the dielectric layer has acolumn-like or needle-like shape instead of the spherical shapedescribed above, and these grains are densely arranged and piled. Inthis columnar structure the crystal grains grown into a columnar shapeare extending along with a direction of the film thickness of thedielectric layer.

Additionally, in the existing laminated ceramic capacitor, reduction inthe capacitance owing to DC bias application has been suppressed bycontaining, in barium titanate that is a dielectric material, at leastone kind or more selected from Fe, Co, Ni, Cu, and Zn in addition to Al(see WO02011/027625).

Moreover, insulation resistance of the thin film capacitor has beenimproved by doping Al to a dielectric thin film of barium strontiumtitanate type to reduce leak current characteristics of the thin filmcapacitor (see Japanese Unexamined Patent Publication No. 2014-144881).

Further, in a dielectric layer having a perovskite crystal structurerepresented by a formula of a crystal structure A_(y)BO₃ (A: A siteelement, B: B site element, O: oxygen, y: ratio of A site element/B siteelement), biased humidity reliability of the capacitor has been improvedby defining 0.97≦y<1.00 (see Japanese Unexamined Patent Publication No.2010-267953).

Study on capacitance improvement, insulation resistance improvement, andbiased humidity reliability enhancement of the thin film capacitor hasbeen made, but, as the dielectric layer of the thin film capacitorhaving the columnar structure becomes thinned, it has been difficult tosuppress the reduction in the capacitance owing to DC bias applicationwhile maintaining the capacitance, the insulation resistance, and thebiased humidity reliability.

Then, an object of the present invention is to provide a thin filmcapacitor having a fine structure called the columnar structure in adielectric layer of the perovskite crystal structure of A_(y)BO₃(y≦0.995), in which the reduction in the capacitance owing to DC biasapplication is suppressed.

The above problem is solved by a thin film capacitor comprising a basematerial, a dielectric layer provided on the base material, and an upperelectrode layer provided on the dielectric layer, in which thedielectric layer includes a plurality of columnar crystals that extendalong a normal direction with respect to an surface of the upperelectrode layer, the columnar crystal has a perovskite crystal structurerepresented by A_(y)BO₃, an element A is at least one of Ba, Ca, Sr, andPb, an element B is at least one of Ti, Zr, Sn, and Hf, y≦0.995 issatisfied, and the dielectric layer contains 0.05 to 2.5 mol of Al per100 mol of A_(y)BO₃. If y≦0.995 holds, the A site element which isexcess and does not react to the B site element is not generated in thefilm. If the excess A site element exists in the film, it reacts tooxygen and carbon dioxide in the air to generate carbonate derived fromthe A site element in the film. Carbonate has water absorbability, andthus, is considered to have adverse effects on the biased humidityreliability. Therefore, if y≦0.995 holds, the excess A site element isprevented from generating to improve the biased humidity reliability.Moreover, if y<0.97 holds, insulation resistance of the dielectric layertends to decrease. For this reason, if 0.97≦y≦0.995 holds, the biasedhumidity reliability is improved and the insulation resistance isfurther improved at the same time.

The A site element and the B site element are selected from a viewpointthat A_(y)BO₃ may form the perovskite crystal structure and itsdielectric constant becomes high. Additionally, in the dielectric layerof the perovskite crystal structure represented by A_(y)BO₃ with y≦0.995made of the columnar crystals whose elements are selected as describedabove, containing 0.05 mol or more of Al per 100 mol of A_(y)BO₃ allowsDC bias dependence of the capacitance to be suppressed even in thecolumnar structure having large capacitance. This was considered becausecontaining Al in a proper amount weakens ferroelectricity of theperovskite crystal structure of the dielectric layer, suppressing the DCbias dependence of the capacitance. Further, it can be considered thatcontaining Al in a proper amount promotes a structure that thedielectric layer has a dense fine structure, that is, the columnarstructure, suppressing the reduction in the capacitance. However, if theAl content is large, the dielectric constant of the dielectric layer maybe reduced. Therefore, the Al content is required to be 2.5 mol or less.

Further, the dielectric layer may contain 0.05 to 0.45 mol of Mn per 100mol of A_(y)BO₃. In addition, at least one of V, Nb, and Ta may becontained in an amount of 0.05 to 0.5 mol in total. Moreover, at leastone of rare-earth elements may be contained in an amount of 0.05 to 0.3mol in total. The rare earth element can be particularly at least one ormore selected from Y, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb.These elements may be contained together with Al, which may improve alsothe insulation resistance and the biased humidity reliability at thesame time to further enhance the effect of the invention. Moreover, ify<0.97 holds, the insulation resistance of the dielectric layer tends toreduce. For this reason, if 0.97≦y≦0.995 holds, the biased humidityreliability is improved and the insulation resistance is furtherimproved at the same time.

Moreover, a metal foil containing 50 wt % or more of Ni as a principalcomponent is used as the base material, facilitating thinning of thethin film capacitor in thickness. Since coefficients of thermalexpansion of the dielectric layer formed on the base material and themetal foil containing Ni are similar values, a stress applied from thebase material to the dielectric layer can be relaxed to suppress thereduction in the capacitance. In addition, it can be considered that afailure between the base material and the dielectric layer such asseparation or crack caused by temperature shock and the like may bedecreased.

By containing Al in the dielectric layer having the columnar structure,the reduction in the capacitance owing to DC bias application can besuppressed as compared with a dielectric layer which has the columnarstructure not containing Al.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a thin film capacitoraccording to an embodiment of the invention;

FIG. 2 is a schematic cross-sectional view of a thin film capacitoraccording to another embodiment of the invention;

FIG. 3 is a transmission electron microscope image (TEM image) of across-section of a thin film capacitor according to an embodiment of theinvention (Example 43); and

FIG. 4 is a transmission electron microscope image (TEM image) of across-section of a thin film capacitor which does not belong to theembodiment of the invention (Comparative example 19).

DETAILED DESCRIPTION

Hereinafter, a description is given of preferred embodiments of thepresent invention with reference to the drawings. However, the inventionis not limited to the following embodiments, and each followingembodiment shows an example of aspects belonging to a technical scope ofthe invention. Note that the same or similar components are designatedby the same reference sign in each drawing and the duplicateddescription thereof is omitted.

A cross-sectional structural view of a thin film capacitor according tothe embodiment is shown in FIG. 1 and FIG. 2. A base material 1supporting a dielectric layer 2 may have an electrode layer on asurface. The thickness of the electrode layer can be between 0.01 and100 μm. This base material can be those formed in such a way that athermal oxide film of SiO₂ or the like is formed on a Si substrate,subsequently a nitride or oxide layer of TiO₂, TiN or the like, or aconductive oxide layer of LaNiO₃ or the like is formed thereon, andthereafter, an electrode layer made of noble metal such as Au, Ag, Pt,Pd, Rh, Ir, Ru, and Os, or metal such as Ni and Cu, or an alloy whichcontains Ni as a principal component, or a composite structure whichcontains various metals is formed. Moreover, the base material may beformed by using a ceramic substrate of Al₂O₃ or the like in place of theSi substrate and forming the electrode layer thereon. Further, theelectrode layer may be made of not metal but a conductive oxide, forexample, so long as it is a conductive layer. Still further, theelectrode layer may have a structure in which two or more layers of themetal or alloy described above are laminated.

A method for forming the electrode layer described above may be, forexample, a method using a chemical solution such as a SolGel method, anda MOD (Metal Organic Decomposition) method, a gas phase method such asMOCVD method, a CVD method, sputtering and a PLD (Pulse LaserDeposition) method, or an evaporation method.

Further, the base material 1 may be a metal foil. It is preferable themetal foil is a metal foil containing 50 wt % or more of Ni as aprincipal component. In the case of using the metal foil, it isadvantageous that the thin film capacitor can be thinned, or that sincea coefficient of thermal expansion of the metal foil has a value nearthat of the dielectric layer 2 formed on the base material 1, a stressapplied from the base material 1 to the dielectric layer 2 can berelaxed to suppress reduction in the capacitance. In addition, it can beconsidered that a failure between the base material 1 and the dielectriclayer 2 such as separation or crack caused by temperature shock and thelike may be decreased.

The dielectric layer 2 may be those having a perovskite crystalstructure represented by a formula of a crystal structure A_(y)BO₃ (A: Asite element, B: B site element, O: oxygen, y: ratio of A site element/Bsite element). It is preferable that y≦0.995 holds in order to achievebiased humidity reliability. A columnar structure can exist all over thedielectric layer 2.

The A site element may be those containing at least one of Ba, Ca, Srand Pb. The B site element may be those containing at least one of Ti,Zr, Sn and Hf. In order to decrease the reduction in the capacitanceowing to DC bias application to the thin film capacitor, the dielectriclayer 2 may contain 0.05 mol to 2.5 mol of Al per 100 mol of A_(y)BO₃.Moreover, 0.05 to 0.45 mol of Mn may be contained per 100 mol ofA_(y)BO₃. Further, 0.05 to 0.5 mol in total of at least one of V, Nb andTa which are pentavalent metal may be contained. Additionally, 0.05 to0.3 mol of a rare-earth element may be contained. The rare earth elementmay be particularly at least one or more selected from Y, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb. By containing these elements, thethin film capacitor can be obtained of improved insulation resistance,good biased humidity reliability, and low reduction in the capacitanceowing to DC bias application.

A method for forming the dielectric layer 2 may be a general method formanufacturing a thin film, for example, a method using a chemicalsolution such as a SolGel method, a MOD (Metal Organic Decomposition)method, a gas phase method such as a MOCVD method, a CVD method,sputtering and a PLD (Pulse Laser Deposition) method, or an evaporationmethod.

It is preferable that a film thickness of the dielectric layer 2 is 100nm to 1000 nm. This is because if the thickness is thinner than 100 nm,in a case where DC bias is applied to the thin film capacitor, anexcessive electric field intensity may be applied to deteriorate theinsulation resistance so that a function as a capacitor is not possiblyexerted. On the other hand, as a reason for the above, if the thicknessexceeds 1000 nm, the capacitance of the capacitor per unit area isreduced to make it difficult to manufacture a capacitor of highcapacitance.

An upper electrode layer 3 may use the electrode layer used for the basematerial 1 or the same type as the base material 1 itself; and Ni, Cu orthe like is preferable. In addition, Al which is large in electricconductivity may be used. Moreover, the noble metal such as Au, Ag, Pt,Pd, Rh, Ir, Ru and Os may be used. Further, alloy or composite includingthe above metal may be used. Still further, the upper electrode layer 3may be a laminated body of two or more layers including the above metal,alloy, or composite. Yet further, as for a method for forming the upperelectrode layer 3, a method of the same type as the method for formingthe dielectric layer 2 may be used.

In a case where the thin film capacitor is formed into an element, aneed to form an insulating layer 6 covering a capacitor part of theelement is brought about. This insulating layer 6 may preferably use,for example, insulating resin such as a polyimide type resin, an epoxytype resin, a phenol type resin, a benzocyclobutene type resin, apolyamide type resin and a fluoropolymer type resin. Additionally, aninorganic material such as SiO₂ may be used.

Moreover, in the case where the thin film capacitor is formed into anelement, as shown in FIG. 2, a need to form extraction electrodes 4 isbrought about for extracting electrodes from the base material 1 sideand from the upper electrode layer 3 side. These extraction electrodes 4can be fabricated by means of sputtering, plating or the like and metalof the same type as the upper electrode layer 3 may be used as materialsthereof. Futher, terminal electrodes 5 need to be formed, and theseterminal electrodes 5 can be fabricated by means of plating or the likeand metal of the same type as the upper electrode layer 3 may be used asmetal used therefor. Still further, in order to improve contact betweenthe insulating layer 6 and the terminal electrode 5 or the extractionelectrode 4, a contact layer made of Ti, Cr or the like may be formedbetween the insulating layer 6 and the extraction electrode 4 andbetween the insulating layer 6 and the terminal electrode 5.

Hereinafter, a description is given in more detail of the inventionthrough Examples and Comparative example. However, the invention is notlimited to Examples and Comparative examples below.

EXAMPLES, COMPARATIVE EXAMPLES

A Ni foil substrate of 100×100 mm was prepared. The Ni foil whosesurface was polished was used because the dielectric layer was formedthereon. The dielectric layer was formed on the polished surface side ofthe Ni foil by means of a solution technique. As a material solution, abutanol solution was used in which barium octylate, strontium octylate,calcium octylate, titanium octylate, zirconium octylate, aluminumoctylate, manganese octylate, vanadium octylate, niobium octylate,tantalum octylate, and yttrium octylate were solved. Respective materialsolutions were weighed and prepared to obtain compositions in Table 1 toTable 4. The concentration of the prepared solution was adjusted to be0.6 mol/kg in terms of Ti content by adding the butanol solution. Theprepared solution was coated on the Ni foil surface by spin coating.After coating, a solvent in the applied film was dried and removed at150° C., and was heated in an air atmosphere at 400° C. for 10 minutesto decompose the octylic acid. After that, the resultant was heated invacuum (10⁻³ to 10⁻⁴ Pa) at 900° C. for 30 minutes to crystallize theapplied film. A crystallized dielectric layer was formed, followed byapplication of the prepared solution again by spin coating to besubjected to the above series of operations until the crystallization.This series of operations from the solution application until thecrystallization was repeated 15 times, that is, repeated until a targetdielectric layer thickness was obtained. Through this process, thedecomposition and crystallization of the solution was promoted withrespect to a layer applied on each of 15 layers so as to promotecolumnar crystallization. The resultant film thickness was 800 nm.Compositional analysis of the film using fluorescent X-rays wasperformed to confirm that the composition of the crystallized film isthe same as the feed composition of each of the solutions in Table 1 toTable 4. Further, a cross-sectional structure of the dielectric layerwas observed using a scanning electron microscope (SEM) and atransmission electron microscope (TEM). As a result of the observation,all samples in Table 1 to Table 4 were confirmed to be the dielectriclayer having the columnar structure. As an example, a TEM image of across-sectional structure of a dielectric layer in Example 43 is shownin FIG. 3.

Next, an upper electrode layer was formed by sputtering Ni of 500 nm andCu of 2000 nm on the dielectric layer. Next, in order to fabricate achip-type capacitor element having a size of length 1 mm×width 0.5 mm(1005 element), the upper electrode layer and the dielectric layer werepatterned, and thereafter, an insulating layer was formed of polyimideresin. In forming the insulating layer, in order to form extractionelectrodes from the Ni foil side and the upper electrode layer side, viaholes were formed in the insulating layer by photolithography.

Next, on the insulating layer in which the via holes were formed, a Tilayer of 20 nm was formed by sputtering, and subsequently a Cu layer of500 nm was formed. Cu plating was performed with the Ti layer and the Culayer being used as a seed electrode layer to fabricate the extractionelectrodes in the via holes and then terminal electrodes having apredetermined shape. A thickness of the terminal electrode was 10 μm.After that, the seed electrode layer was removed except for portions ofthe terminal electrodes to fabricate a thin film capacitor of 1005element. On the Ni foil of 100×100 mm 8000 capacitors were formed. Afterthat, a single body of the 1005 element was fabricated by dicing.

The capacitance at no DC loading and insulation resistance of thefinished 1005 element were measured in such a manner that 10 sampleswere measured per one measurement. The capacitance was measured using anLCR meter 4284A manufactured by Agilent Co. at 1 kHz, 1 Vrms, and a roomtemperature. The insulation resistance was measured using ahigh-resistance meter 4339B manufactured by Agilent Co. at DC 4V and aroom temperature. Results of an average of the measured values ofseveral tens of samples are shown in Table 5 to Table 8.

Next, the capacitance at DC bias application was evaluated. The numberof samples per one measurement was ten for each composition. A changerate of the capacitance by DC 5V application relative to the capacitanceat no DC loading was obtained. An average of values of several tens ofsamples is shown in Table 5 to Table 8.

Next, biased humidity reliability characteristic of the sample for eachcomposition was evaluated. The number of the evaluated samples for eachcomposition was 20, and the samples were tested at DC 4 V, 60° C., and95% RH for 2000 hours. The insulation resistances of the samples beforeand after the test were measured at DC 4V, and those of the samples notreduced in the insulation resistance to 1/50 of that before the testwere determined as good products. A ratio of the samples determined as agood product even after the test is shown in Table 5 to Table 8.

In a case of Al content in a range of 0.05 to 2.5 mol %, the reductionin the capacitance in DC bias application was −40% or less, showing agood result (Examples 1 to 15, Examples 16 to 30, Examples 31 to 45,Examples 46 to 60, and Examples 61 to 64). It was found that a casewhere the Al content is less than 0.05 mol % has a problem in that thereduction in the capacitance owing to DC bias application exceeds 40%and the capacitance of the capacitor would be remarkably reduced if DCbias is applied (Comparative example 1, Comparative example 4,Comparative example 7, Comparative example 8, Comparative examples 10 to11, Comparative examples 13 to 14, Comparative examples 16 to 17, andComparative example 19). Moreover, it was found that in a case where theAl content exceeds 2.5 mol %, the capacitance of the capacitor fallsbelow 2 nF and the biased humidity reliability is not kept at all(Comparative example 9, Comparative example 12, Comparative example 15,Comparative example 18, and Comparative example 20).

Further, it was found that in a case where Mn, the pentavalent metals V,Nb and Ta, and Y as one of the rare-earth elements are containedtogether with Al at the same time, a remarkable effect is given to theinsulation resistance and biased humidity reliability of the capacitor,and the capacitor in which DC bias dependence of the capacitance is lowcan be obtained. As for content, it was found that Mn content, totalcontent of the pentavalent metals V, Nb and Ta, and Y content as one ofthe rare-earth elements may be respectively 0.05 to 0.45 mol %, 0.05 to0.5 mol %, and 0.05 to 0.3 mol % (Examples 1 to 6, Examples 13 to 15,Examples 16 to 21, Examples 28 to 30, Examples 31 to 36, Examples 43 to45, Examples 46 to 51, Examples 58 to 60, Examples 61 to 64). In a caseof the contents out of the above range, the reduction in the insulationresistance was remarkable, the biased humidity reliabilitycharacteristic was deteriorated, or the capacitance was reduced.

Further, if y that is the ratio of A site element /B site element is0.995 or less, the biased humidity reliability characteristic is alsoimproved. Therefore, y is required to be 0.995 or less. It was foundthat if y is 1 or more, the biased humidity reliability is not kept atall (Comparative examples 1 to 6). In addition, if y is 0.96 or less,the insulation resistance is slightly reduced. For this reason, it ispreferable that 0.97≦y≦0.995 holds. The amounts of Al, Mn, V, Nb, Ta andY in tables 1 to 4 and 9 are “mol %” relative to 1 mol of(Ba_(1-a-b)Sr_(a)Ca_(b))_(y)Ti_(1-c)Zr_(c)O₃.

TABLE 1 (Ba_(1−a−b)Sr_(a)Ca_(b))_(y)Ti_(1−c)Zr_(c)O₃ Al MN V Nb Ta Y a by c (mol %) 1 Comparative 0 0 1.01 0 0 0.2 0.2 0 0 0.1 example 1 2Comparative 0 0 1.01 0 1 0.2 0.2 0 0 0.1 example 2 3 Comparative 0 01.01 0 2 0.2 0.2 0 0 0.1 example 3 4 Comparative 0 0 1 0 0 0.2 0.2 0 00.1 example 4 5 Comparative 0 0 1 0 1 0.2 0.2 0 0 0.1 example 5 6Comparative 0 0 1 0 2 0.2 0.2 0 0 0.1 example 6 7 Comparative 0 0 0.9950 0 0.2 0.2 0 0 0.1 example 7 8 Comparative 0 0 0.995 0 0.03 0.2 0.2 0 00.1 example 8 9 Example 1 0.03 0 0.995 0 0.05 0.45 0.05 0 0 0.1 10Example 2 0 0.03 0.995 0 1.5 0.2 0.1 0.1 0 0.2 11 Example 3 0 0 0.9950.01 1 0.05 0.5 0 0 0.25 12 Example 4 0 0 0.995 0.01 1.5 0.2 0.1 0 0 0.313 Example 5 0 0 0.995 0 0.5 0.5 0 0.05 0.05 0.1 14 Example 6 0 0 0.9950 1.5 0.2 0.3 0.1 0.1 0.1 15 Example 7 0.03 0 0.995 0 0.5 0.2 0.1 0 0.10 16 Example 8 0 0 0.995 0 0.2 0 0 0 0 0 17 Example 9 0 0 0.995 0 0.30.2 0 0 0 0 18 Example 10 0 0 0.995 0 0.5 0.2 0 0 0 0.1 19 Example 11 00 0.995 0 0.5 0 0.2 0 0 0 20 Example 12 0 0 0.995 0 0.5 0 0.2 0 0 0.1 21Example 13 0 0 0.995 0 1 0.2 0.2 0 0 0.05 22 Example 14 0 0 0.995 0 20.2 0.2 0 0 0.1 23 Example 15 0 0 0.995 0 2.5 0.2 0.2 0 0 0.1 24Comparative 0 0 0.995 0 3 0.2 0.2 0 0 0.1 example 9

TABLE 2 (Ba_(1−a−b)Sr_(a)Ca_(b))_(y)Ti_(1−c)Zr_(c)O₃ Al Mn V Nb Ta Y a by c (mol %) 25 Comparative 0 0 0.99 0 0 0.2 0.2 0 0 0.1 example 10 26Comparative 0 0 0.99 0 0.03 0.2 0.2 0 0 0.1 example 11 27 Example 160.03 0 0.99 0 0.05 0.45 0.05 0 0 0.1 28 Example 17 0 0.03 0.99 0 1.5 0.20.1 0.1 0 0.2 29 Example 18 0 0 0.99 0.01 1 0.05 0.5 0 0 0.25 30 Example19 0 0 0.99 0.01 1.5 0.2 0.1 0 0 0.3 31 Example 20 0 0 0.99 0 0.5 0.5 00.05 0.05 0.1 32 Example 21 0 0 0.99 0 1.5 0.2 0.3 0.1 0.1 0.1 33Example 22 0.03 0 0.99 0 0.5 0.2 0.1 0 0.1 0 34 Example 23 0 0 0.99 00.2 0 0 0 0 0 35 Example 24 0 0 0.99 0 0.3 0.2 0 0 0 0 36 Example 25 0 00.99 0 0.5 0.2 0 0 0 0.1 37 Example 26 0 0 0.99 0 0.5 0 0.2 0 0 0 38Example 27 0 0 0.99 0 0.5 0 0.2 0 0 0.1 39 Example 28 0 0 0.99 0 1 0.20.2 0 0 0.05 40 Example 29 0 0 0.99 0 2 0.2 0.2 0 0 0.1 41 Example 30 00 0.99 0 2.5 0.2 0.2 0 0 0.1 42 Comparative 0 0 0.99 0 3 0.2 0.2 0 0 0.1example 12

TABLE 3 (Ba_(1−a−b)Sr_(a)Ca_(b))_(y)Ti_(1−c)Zr_(c)O₃ Al Mn V Nb Ta Y a by c (mol %) 43 Comparative 0 0 0.98 0 0 0.2 0.2 0 0 0.1 example 13 44Comparative 0 0 0.98 0 0.03 0.2 0.2 0 0 0.1 example 14 45 Example 310.03 0 0.98 0 0.05 0.45 0.05 0 0 0.1 46 Example 32 0 0.03 0.98 0 1.5 0.20.1 0.1 0 0.2 47 Example 33 0 0 0.98 0.01 1 0.05 0.5 0 0 0.25 48 Example34 0 0 0.98 0.01 1.5 0.2 0.1 0 0 0.3 49 Example 35 0 0 0.98 0 0.5 0.5 00.05 0.05 0.1 50 Example 36 0 0 0.98 0 1.5 0.2 0.3 0.1 0.1 0.1 51Example 37 0.03 0 0.98 0 0.5 0.2 0.1 0 0.1 0 52 Example 38 0 0 0.98 00.2 0 0 0 0 0 53 Example 39 0 0 0.98 0 0.3 0.2 0 0 0 0 54 Example 40 0 00.98 0 0.5 0.2 0 0 0 0.1 55 Example 41 0 0 0.98 0 0.5 0 0.2 0 0 0 56Example 42 0 0 0.98 0 0.5 0 0.2 0 0 0.1 57 Example 43 0 0 0.98 0 1 0.20.2 0 0 0.05 58 Example 44 0 0 0.98 0 2 0.2 0.2 0 0 0.1 59 Example 45 00 0.98 0 2.5 0.2 0.2 0 0 0.1 60 Comparative 0 0 0.98 0 3 0.2 0.2 0 0 0.1example 15

TABLE 4 (Ba_(1−a−b)Sr_(a)Ca_(b))_(y)Ti_(1−c)Zr_(c)O₃ Al Mn V Nb Ta Y a by c (mol %) 61 Comparative 0 0 0.97 0 0 0.2 0.2 0 0 0.1 example 16 62Comparative 0 0 0.97 0 0.03 0.2 0.2 0 0 0.1 example 17 63 Example 460.03 0 0.97 0 0.05 0.45 0.05 0 0 0.1 64 Example 47 0 0.03 0.97 0 1.5 0.20.1 0.1 0 0.2 65 Example 48 0 0 0.97 0.01 1 0.05 0.5 0 0 0.25 66 Example49 0 0 0.97 0.01 1.5 0.2 0.1 0 0 0.3 67 Example 50 0 0 0.97 0 0.5 0.5 00.05 0.05 0.1 68 Example 51 0 0 0.97 0 1.5 0.2 0.3 0.1 0.1 0.1 69Example 52 0.03 0 0.97 0 0.5 0.2 0.1 0 0.1 0 70 Example 53 0 0 0.97 00.2 0 0 0 0 0 71 Example 54 0 0 0.97 0 0.3 0.2 0 0 0 0 72 Example 55 0 00.97 0 0.5 0.2 0 0 0 0.1 73 Example 56 0 0 0.97 0 0.5 0 0.2 0 0 0 74Example 57 0 0 0.97 0 0.5 0 0.2 0 0 0.1 75 Example 58 0 0 0.97 0 1 0.20.2 0 0 0.05 76 Example 59 0 0 0.97 0 2 0.2 0.2 0 0 0.1 77 Example 60 00 0.97 0 2.5 0.2 0.2 0 0 0.1 78 Comparative 0 0 0.97 0 3 0.2 0.2 0 0 0.1example 18 79 Comparative 0 0 0.96 0 0 0.2 0.2 0 0 0.1 example 19 80Example 61 0 0 0.96 0 0.5 0.2 0.2 0 0 0.1 81 Example 62 0 0 0.96 0 1 0.20.2 0 0 0.05 82 Example 63 0 0 0.96 0 2 0.2 0.2 0 0 0.1 83 Example 64 00 0.96 0 2.5 0.2 0.2 0 0 0.1 84 Comparative 0 0 0.96 0 3 0.2 0.2 0 0 0.1example 20

TABLE 5 Biased humidity Capacitance reliability Capac- Insulation changerate Number itance resistance by DC bias conforming/ (nF) (Ω) (%) Numberinput 1 Comparative 4.04 3.8 × 10¹⁰ −51.00  0/20 example 1 2 Comparative3.81 8.9 × 10⁹  −37.46  0/20 example 2 3 Comparative 2.80 2.3 × 10⁸ −35.13  0/20 example 3 4 Comparative 4.12 2.2 × 10¹⁰ −51.5  0/20 example4 5 Comparative 3.85 9.8 × 10⁹  −33.39  0/20 example 5 6 Comparative2.96 8.3 × 10⁸  −36.30  0/20 example 6 7 Comparative 4.20 3.1 × 10¹⁰−52.35 20/20 example 7 8 Comparative 4.18 3.0 × 10¹⁰ −51.21 20/20example 8 9 Example 1 4.13 4.0 × 10¹⁰ −39.79 20/20 10 Example 2 4.01 3.2× 10¹⁰ −38.92 20/20 11 Example 3 3.89 2.1 × 10¹⁰ −32.46 20/20 12 Example4 2.89 1.3 × 10¹⁰ −39.79 20/20 13 Example 5 2.88 1.5 × 10¹⁰ −35.61 20/2014 Example 6 2.68 1.2 × 10¹⁰ −33.86 20/20 15 Example 7 4.01 1.1 × 10¹⁰−38.92 18/20 16 Example 8 3.81 2.3 × 10⁷  −36.48 15/20 17 Example 9 3.802.1 × 10¹⁰ −35.32 12/20 18 Example 10 3.80 1.5 × 10¹⁰ −34.74 14/20 19Example 11 3.89 3.2 × 10⁸  −36.19 13/20 20 Example 12 3.88 3.6 × 10⁸ −36.77 12/20 21 Example 13 3.73 1.2 × 10⁹  −30.88 20/20 22 Example 143.00 2.0 × 10⁹  −30.17 20/20 23 Example 15 2.50 2.3 × 10⁹  −29.81 12/2024 Comparative 1.80 2.0 × 10⁹  −27.91  0/20 example 9

TABLE 6 Biased humidity Capacitance reliability Capac- Insulation changerate Number itance resistance by DC bias conforming/ (nF) (Ω) (%) Numberinput 25 Comparative 4.22 3.0 × 10¹⁰ −58.83 20/20 example 10 26Comparative 4.18 2.9 × 10¹⁰ −57.81 20/20 example 11 27 Example 16 4.232.9 × 10¹⁰ −40.66 20/20 28 Example 17 3.94 2.5 × 10¹⁰ −35.04 20/20 29Example 18 3.98 2.0 × 10¹⁰ −38.04 20/20 30 Example 19 2.99 4.3 × 10¹⁰−35.95 20/20 31 Example 20 2.82 3.8 × 10¹⁰ −37.94 20/20 32 Example 212.47 3.1 × 10¹⁰ −35.66 20/20 33 Example 22 4.02 2.1 × 10¹⁰ −38.33 19/2034 Example 23 3.85 1.3 × 10⁷  −36.77 14/20 35 Example 24 3.88 1.2 × 10¹⁰−35.90 12/20 36 Example 25 3.86 1.3 × 10¹⁰ −36.19 15/20 37 Example 263.94 1.1 × 10⁸  −36.48 11/20 38 Example 27 3.83 1.0 × 10⁸  −36.48 10/2039 Example 28 3.79 1.5 × 10¹⁰ −37.75 20/20 40 Example 29 2.93 2.5 × 10⁹ −33.75 20/20 41 Example 30 2.20 2.0 × 10⁹  −30.21 11/20 42 Comparative1.63 1.5 × 10⁹  −29.50  0/20 example 12

TABLE 7 Biased humidity Capacitance reliability Capac- Insulation changerate Number itance resistance by DC bias conforming/ (nF) (Ω) (%) Numberinput 43 Comparative 4.17 2.8 × 10¹⁰ −57.48 20/20 example 13 44Comparative 4.15 2.7 × 10¹⁰ −56.98 20/20 example 14 45 Example 31 4.232.5 × 10¹⁰ −40.66 20/20 46 Example 32 4.00 2.2 × 10¹⁰ −36.83 20/20 47Example 33 3.88 1.8 × 10¹⁰ −37.46 20/20 48 Example 34 2.89 1.2 × 10¹⁰−32.70 20/20 49 Example 35 2.87 1.0 × 10¹⁰ −35.61 20/20 50 Example 362.51 2.2 × 10¹⁰ −31.83 20/20 51 Example 37 4.22 1.8 × 10¹⁰ −34.95 19/2052 Example 38 3.79 1.0 × 10⁸  −37.06 12/20 53 Example 39 3.81 1.5 × 10¹⁰−36.77 11/20 54 Example 40 3.79 1.2 × 10¹⁰ −36.48 16/20 55 Example 413.90 1.2 × 10⁸  −37.06 10/20 56 Example 42 3.89 1.0 × 10⁸  −36.19 12/2057 Example 43 3.73 1.8 × 10¹⁰ −35.08 20/20 58 Example 44 2.88 2.4 × 10⁹ −35.92 20/20 59 Example 45 2.20 1.8 × 10⁹  −32.31 11/20 60 Comparative1.52 1.1 × 10⁹  −29.30  0/20 example 15

TABLE 8 Biased humidity Capacitance reliability Capac- Insulation changerate Number itance resistance by DC bias conforming/ (nF) (Ω) (%) Numberinput 61 Comparative 4.14 2.8 × 10¹⁰ −57.48 20/20 example 16 62Comparative 4.12 2.7 × 10¹⁰ −56.98 20/20 example 17 63 Example 46 4.162.2 × 10¹⁰ −41.83 20/20 64 Example 47 4.02 2.0 × 10¹⁰ −38.13 20/20 65Example 48 3.82 1.5 × 10¹⁰ −39.66 20/20 66 Example 49 2.99 2.8 × 10¹⁰−33.86 20/20 67 Example 50 2.82 1.8 × 10¹⁰ −36.77 20/20 68 Example 512.62 1.3 × 10¹⁰ −34.74 20/20 69 Example 52 4.13 1.0 × 10¹⁰ −38.04 19/2070 Example 53 3.77 2.1 × 10⁷  −37.17 15/20 71 Example 54 3.77 2.1 × 10¹⁰−37.56 13/20 72 Example 55 3.75 1.5 × 10¹⁰ −37.06 18/20 73 Example 563.82 1.2 × 10⁸  −37.35 12/20 74 Example 57 3.73 1.5 × 10⁸  −37.94 10/2075 Example 58 3.66 1.5 × 10¹⁰ −35.11 20/20 76 Example 59 2.89 1.4 × 10⁹ −34.98 20/20 77 Example 60 2.21 1.3 × 10⁹  −30.11 10/20 78 Comparative1.40 9.3 × 10⁸  −28.80  0/20 example 18 79 Comparative 4.10 3.0 × 10⁸ −63.51 20/20 example 19 80 Example 61 4.13 2.3 × 10⁸  −38.83 20/20 81Example 62 4.11 1.2 × 10⁸  −35.66 20/20 82 Example 63 3.10 1.0 × 10⁸ −30.20 17/20 83 Example 64 2.21 8.8 × 10⁷  −29.87 11/20 84 Comparative1.25 8.5 × 10⁷  −28.78  0/20 example 20

Next, similarly, a Ni foil substrate of 100×100 mm was prepared. Asurface of the Ni foil was polished because the dielectric layer wasformed thereon. The dielectric layer of 800 nm was formed on the Ni foilwhose surface was polished by means of a solution technique. As amaterial solution, a butanol solution was used in which barium octylate,titanium octylate, aluminum octylate, manganese octylate, vanadiumoctylate, and yttrium octylate were solved. Respective materialsolutions were weighed and prepared to obtain compositions in Table 9.The concentration of the prepared solution was adjusted to be 0.6 mol/kgin terms of Ti content by adding the butanol solution to the solvent.The prepared solution was coated on the Ni foil surface by spin coating.After coating, the solvent in the applied film was dried and removed at150° C., and was heated in an air atmosphere at 400° C. for 10 minutesto decompose the octylic acid. Application of the solution, drying ofthe applied film, and decomposition of octylic acid were repeated 15times. After that, the resultant was heated in vacuum (10⁻³ to 10⁻⁴ Pa)at 900° C. for 30 minutes to crystallize the applied film. Through thisprocess, columnar crystallization was suppressed. The resultant filmthickness was 800 nm. Compositional analysis of the film usingfluorescent X-rays was performed to confirm that the composition of thecrystallized film is the same as the feed composition of each of thesolutions in Table 9. Further, a cross-sectional structure of thedielectric layer was observed using a scanning electron microscope (SEM)and a transmission electron microscope (TEM). As a result of theobservation, all compositions in Table 9 were confirmed to be thedielectric layer having the granular structure. As an example, a TEMimage of a cross-sectional structure of a dielectric layer inComparative example 19 is shown in FIG. 4.

Next, an upper electrode layer was formed by sputtering Ni of 500 nm andCu of 2000 nm on the dielectric layer. Next, in order to fabricate achip-type capacitor element having a size of length 1 mm×width 0.5 mm(1005 element), the upper electrode layer and the dielectric layer werepatterned, and thereafter, an insulating layer was formed of polyimideresin. In forming the insulating layer, in order to form an extractionelectrode from the Ni foil side and the upper electrode layer side, viaholes were formed in the insulating layer by photolithography.

Next, on the insulating layer in which the via holes were formed, a Tilayer of 20 nm was formed by sputtering, and subsequently a Cu layer of500 nm was formed. Cu plating was performed with the Ti layer and the Culayer being used as a seed electrode layer to fabricate the extractionelectrodes in the via holes and then terminal electrodes having apredetermined shape. A thickness of the terminal electrode was 10 μm.After that, the seed electrode layer was removed except for portions ofthe terminal electrodes to fabricate a thin film capacitor of 1005element. On the Ni foil of 100×100 mm 8000 capacitors were formed. Afterthat, a single body of the 1005 element was fabricated by dicing.

The capacitance at no DC loading and insulation resistance of thefinished 1005 element were measured in such a manner that 10 sampleswere measured per one measurement. The capacitance was measured using anLCR meter 4284A manufactured by Agilent Co. at 1 kHz, 1 Vrms, and a roomtemperature. The insulation resistance was measured using ahigh-resistance meter 4339B manufactured by Agilent Co. at DC 4V and aroom temperature. Results of an average of the measured values ofseveral tens of samples are shown in Table 10.

Next, the capacitance at DC bias application was evaluated. The numberof samples per one measurement was ten for each composition. A changerate of the capacitance by DC 5V application relative to the capacitanceat no DC loading was obtained. An average of values of several tens ofsamples is shown in Table 10.

Next, the biased humidity reliability of the sample for each compositionwas evaluated. The number of the evaluated samples for each compositionwas 20, and the samples were tested at DC 4 V, 60° C., and 95% RH for2000 hours. The insulation resistances of the samples before and afterthe test were measured at DC 4V, and those of the samples not reduced inthe insulation resistance to 1/50 of that before the test were evaluatedas good products. A ratio of the samples determined as a good producteven after the test is shown in Table 10.

TABLE 9 (Ba_(1−a−b)Sr_(a)Ca_(b))_(y)Ti_(1−c)Zr_(c)O₃ Al Mn V Nb Ta Y a by c (mol %) 85 Comparative 0 0 0.995 0 1 0.2 0.2 0 0 0.1 example 21 86Comparative 0 0 0.99 0 1 0.2 0.2 0 0 0.1 example 22 87 Comparative 0 00.98 0 1 0.2 0.2 0 0 0.1 example 23 88 Comparative 0 0 0.97 0 1 0.2 0.20 0 0.1 example 24

TABLE 10 Biased humidity Capacitance reliability Capac- Insulationchange rate Number itance resistance by DC bias conforming/ (nF) (Ω) (%)Number input 85 Comparative 2.81 1.2 × 10¹⁰ −37.5 0/20 example 21 86Comparative 2.75 1.1 × 10¹⁰ −38.2 0/20 example 22 87 Comparative 2.741.8 × 10¹⁰ −39.1 0/20 example 23 88 Comparative 2.30 1.1 × 10¹⁰ −39.80/20 example 24

These thin film capacitors are in a preferable scope of the invention asfor a composition range of the dielectric layer, but reduced in thecapacitance as compared with a thin film capacitor having the dielectriclayer of the columnar structure because the fine structure of the filmis the granular structure. Further, it was found that the biasedhumidity reliability is not kept at all. Containing Al has the similareffect on the reduction in the capacitance in DC bias application, butthe biased humidity reliability is deteriorated. For this reason, thefine structure of the film is required to have the columnar structure.

What is claimed is:
 1. A thin film capacitor comprising: a basematerial; a dielectric layer provided on the base material; and an upperelectrode layer provided on the dielectric layer, wherein the dielectriclayer includes a plurality of columnar crystals that extend along anormal direction with respect to a surface of the upper electrode layer,the columnar crystals have a perovskite crystal structure represented byA_(y)BO₃, an element A is at least one of Ba, Ca, Sr, and Pb, an elementB is at least one of Ti, Zr, Sn, and Hf, y≦0.995 is satisfied, and thedielectric layer contains 0.3 to 2.5 mol of Al per 100 mol of A_(y)BO₃.2. The thin film capacitor according to claim 1, wherein the dielectriclayer further contains 0.05 to 0.45 mol of Mn per 100 mol of A_(y)BO₃.3. The thin film capacitor according to claim 1, wherein the dielectriclayer further contains at least one of V, Nb, and Ta, and total contentof V, Nb, and Ta is 0.05 to 0.5 mol per 100 mol of A_(y)BO₃.
 4. The thinfilm capacitor according to claim 1, wherein the dielectric layerfurther contains at least one of rare-earth elements, and total contentof the rare-earth elements is 0.05 to 0.3 mol per 100 mol of A_(y)BO₃.5. The thin film capacitor according to claim 1, wherein 0.97≦y≦0.995holds.
 6. The thin film capacitor according to claim 1, wherein the basematerial is a metal foil that contains Ni as a principal component.